Reinforcing steel rods are universally used to strengthen concrete. The steel rods are produced in the steel mill by rollers to size the diameter of the rods and also produce a predetermined form of deformation on the outer surface of the rods. These deformations provide the bonding strength of the rod to the concrete when embedded therein. The steel industry has developed standards relative to the strength of reinforcing steel rods and also standards relative to the dimensions of the deformations on the surfaces thereof. However, each steel mill has independently developed deformation specifications which vary the spacing and orientation of the deformations. The spacing and orientations of the deformations therefore provide an indicia for determining the source of the reinforcing rod. In some instances as a result of using various sets of rollers even the same steel mill may have variations in both the spacing and orientation of the deformations while at the same time maintaining the same pattern.
It is also generally known that reinforcing steel rods are placed in a concrete structure in networks which are located at positions dictated by accepted design criteria. When the design criteria dictates that continuity of reinforcing steel is required a number of methods have been developed to meet this criteria. The first method merely involves the selection of a reinforcing rod having the required length. However, economies of production have limited the total length of a single steel rod to approximately sixty feet. The second method is to lap splice two adjoining pieces of reinforcing steel rods. However, a lap splice requires double the space and in areas of very dense reinforcing steel construction there is often not enough space available in relation to the concrete to meet design criteria. This is commonly encountered in columns, walls, piers or other structures that have a rather small volume but require very heavy reinforcing steel rods.
Finally connecting couplings have been developed to directly join two pieces of reinforcing steel rods in an end-to-end relation. Such couplings have taken the form of steel sleeves placed equal distances over both ends of the adjoining reinforcing rods. Molten metal is poured into the spaces defined between the outside of the reinforcing steel rods and the inside of the sleeve in order to bond the sleeve to the rod. Obviously this method is cumbersome and sometimes cannot be relied on to provide the same strength in each coupling. It should be also noted that a fire hazard is always present whenever molten metal must be used to produce a final object.